#include <iostream>
using namespace std;

int main(void)
{
	int num;
	int i, count = 1;
	cin >> num;
	if (num == 0 || num == 1)
	{
		count = 1;
	}
	else
	{
		for (i = num; i > 1; i--)
		{
			count *= i;
		}
	}
	cout << count;

	system("pause");
	return 0;
}